1. The Invention
This invention relates to sulfur cement-aggregate compositions. In a further aspect, the invention relates to sulfur mortars and concretes having superior resistance to freeze-thaw degradation.
2. The Prior Art
Sulfur mortars and concretes generally refer to a mixture of sulfur and aggregate wherein the sulfur functions as the cement or binder. Generally, whether a composition is classed as a mortar or concrete is based on the particle size of the predominate aggregate. Thus, compositions containing larger sized aggregates are generally referred as concretes whereas compositions containing smaller sized aggregate are referred to as mortars. In either case, the compositions can also contain very fine particle size aggregates, such as fly ash, silica flour, etc., as fillers. Sulfur mortars and concretes are prepared by heating sulfur with an aggregate at a sufficient temperature to render the sulfur molten and then allowing the mixture to cool to solidify the sulfur. Not infrequently, the sulfur also contains a plasticizer which desirably modifies the sulfur, probably by reacting with at least a portion of the sulfur. Such sulfur is referred to as plasticized sulfur.
Sulfur mortars and concretes can be broadly classified as sulfur cement products. Sulfur cement is similar to Portland cement in forming concretes or mortars. In the latter case, a mixture of Portland cement and aggregate is solidified into a final solid product by treatment with water. In the case of sulfur products, heat is used to render the sulfur cement molten, which, upon cooling, solidifies, binding the aggregate.
Sulfur cement concretes can be used for many of the same purposes as conventionally formed concretes. For example, sulfur concretes can be used for structural members, roads, slabs, curbings, gutters, and can be precast or cast at the job site. Sulfur cement concrete affords a significant advantage over Portland cement concrete, especially in the case of preformed articles, in that the sulfur cement concrete can be remelted and recast. Thus, when defective or surplus articles are prepared, the sulfur aggregate composition can be reused by merely melting down the article and recasting the composition. Sulfur cement mortars can be used for similar purposes as Portland cement mortars, such as, for example, bonding structural members together. Sulfur cement mortars and concretes also generally have good corrosion resistance to acids and other chemicals.
Sulfur cement mortars and concretes are well known to the art and various modifications are described in the patent literature such as, for example, U.S. Pat. Nos. 2,135,747, 3,954,480, 4,025,352, 4,058,500, and 4,188,230. C. W. Davis in Industrial and Engineering Chemistry, Vol. 19, No. 12, pages 1350-1352 (1927) teaches that pH control including treating bentonite and clays with aqueous hydrochloric acid reduces swelling as compared with water.
As in the case of Portland cement products, sulfur cement products are subject to freeze-thaw degradation, resulting in brittleness, cracking, crumbling, loss of strength or general failure of the product. Thus, it would be very desirable to provide sulfur cement products which have improved resistance to freeze-thaw degradation.